Risks of positive HIV tests in HIV vaccine trials volunteers

Rachel Tompa

Past recipients of HIV vaccines from vaccine trials are likely to test positive for HIV despite not actually being infected, according to new research from VIDD staff scientist Dr. Cristine Cooper and colleagues. Since vaccines work in part by spurring the immune system to produce virus-specific antibodies, there is a possibility that HIV vaccine trial volunteers who were vaccinated may test reactive (positive) for HIV even when they are not infected, since some HIV tests look for those same antibodies as an indication of infection. Getting a positive result on an HIV test may greatly impact these volunteers’ lives, affecting their ability to immigrate to certain countries, or obtain employment or medical insurance. Importantly, it may be difficult for these volunteers, some of whom are at high risk for HIV, to know their true HIV status with certainty if tested outside the study clinic.

To determine how common these vaccine-induced reactive tests are, the researchers looked at data from 2,176 past participants of HVTN trials who had received a candidate HIV vaccine. All participants were given HIV tests at the end of their trials, using three types of FDA-approved HIV tests. Overall, 908 of these volunteers, more than 40 percent of vaccine recipients, had reactive results on one or more of the test types but were not actually HIV infected. However, the scientists saw big differences in reactive rates depending on the type of HIV vaccine received or test used. For example, more than 85 percent of those who received adenovirus 5-based vaccines tested positive, while only 6 percent of those who received DNA-alone vaccines did.

The researchers stress that it is important for all trial participants and their doctors to know whether they show positive results on HIV tests, to reduce future social harms.